This shared instrumentation grant application is to provide funds to purchase a PhosphorImager for use by Public Health Service-funded investigators at the University of Texas Medical Branch (UTMB). Storage phosphor technology is a new technique that is rapidly replacing the traditional methods of autoradiography for detection and quantitation of radioactive isotopes embedded in polyacrylamide gels or immobilized onto nitrocellulose membranes. Autoradiography has been a universal technique used in molecular biological and biochemical experimentation and relies on, and is limited by, the physics of energy transfer between incident radioactive particles and silver halide crystals embedded in a film emulsion. This inefficient energy transfer is due to both the fact that multiple quanta must strike a silver crystal before a stable latent image is formed, and that ninety percent of incident beta particles pass through the screen undetected. Even under optimized conditions to enhance sensitivity of detection by film emulsions, X-ray film demonstrates a narrow range of linear response. Subsequent quantitation of the developed autoradiographic film is performed by scanning laser densitometry, a labor-intensive and time consuming process that depends on empiric (and frequently multiple) film exposures. Storage phosphor technology eliminates this dependence on developed film emulsions for nondestructive autoradiography. Storage phosphor screens trap and store energy from radioactive emissions that can be subsequently activated, digitalized, and quantitated. The advantages of phosphor screens are immense and include a nearly 100% capture efficiency of radioactive emissions from beta and gamma particle emitting isotopes, linear dynamic range of 100,000:1, a 10-100 fold increase in sensitivity compared with equally exposed X-ray film, and exposure and scan time on re-usable cassettes that are a fraction of the time required using currently available (film-based) technology. Presently, this technology is not available on campus. The application of the PhosphorImager to our research will have immediate benefit in the speed and quality at which we can address an major research objectives.